Seasonal growth,density, reproductive phenology and agar quality of Gracilaria sordida (Gracilariales,Rhodophyta) at Mokomoko Inlet,New Zealand

Growth of mesh-enclosed Gracilaria sordida plants was determined monthly for one year at the Mokomoko mudflat, South Island, New Zealand. Growth of plants with permanent water cover was correlated with water temperature and was most rapid during summer months. Plants exposed at low tide grew only during early spring and late autumn. Bimonthly quadrat sampling of a mudflat population showed that all stages of the life cycle were present throughout the year. Spermatangial plant length and biomass were greatest in early spring; cystocarpic and tetrasporic plants were greatest in midsummer. Sterile plants were most numerous in the late summer. Agar yield showed little variation either seasonally or between different stages of the life cycle. Agar gel strengths for all life cycle stages were greatest at the time of peak plant size and abundance. Gels from spermatangial plants generally were weaker than those from other stages.     

Length–weight relationships of eight deep‐sea fish species collected from the southwest coast of India

Length‐weight relationships (LWR) for eight deep‐sea fishes belonging to six families collected from the south west coast of India are presented. Specimens were caught by deep‐sea shrimp trawls with mesh size 24 mm during 2011 and 2013. The b values ranged from 2.13 to 3.71 and the coefficient of determination (r²) ranged from 0.84 to 0.98. A new standard length maximum was recorded for Neoscopelus microchir. The b values estimated during the present study were compared with the values estimated using models based on Bayesian approach deposited in Fish Base.     

Comparison of behavioural development between Japanese flounder (Paralichthys olivaceus) and spotted halibut (Verasper variegatus) during early life stages

Behavioural development was compared between two flatfish species (Japanese flounder and spotted halibut) from hatching to settlement (juvenile stage) in order to speculate on the ecology of their early life stages and to provide fundamental knowledge for improving seedling production techniques for stock enhancement. Fish were cultured under identical rearing conditions (500‐L tank maintained at 17.8 ± 0.4°C, 34 ppt, 10L : 14D light regime and an initial stocking density of 20 larvae L^?1). Behavioural observations were conducted at about 4‐day intervals from hatching to the juvenile stage. Fish were sampled randomly from the rearing tank, and one fish was transferred into a 250‐ml observation container. Behaviour was video‐recorded for 5 min without food and for an additional 5 min with live feed (rotifer or Artemia). All behavioural data were sorted according to eight developmental stages and compared among developmental stages and between species. The average standard length of the spotted halibut was significantly greater than that of the Japanese flounder in all developmental stages, while the development of Japanese flounder was faster than that of the spotted halibut. For Japanese flounder, feeding, swimming and Ohm‐posture (typical shivering behaviour observed during early life stages in flatfishes) frequency were highest before metamorphosis (mean ± SD; 1.0 ± 2.0 attacks min^?1, 24.0 ± 9.6 actions min^?1, 1.1 ± 1.1 counts min^?1, respectively). Spotted halibut expressed feeding behaviour frequently from the beginning of metamorphosis (3.6 ± 5.2 attacks min^?1), had relatively low swimming activity during all developmental stages, and showed a peak of Ohm‐posture frequency during the flexion stage (2.6 ± 1.0 counts min^?1).     

Recruitment and growth of juvenile yellowfin bream, Acanthopagrus australis Günther (Sparidae), in an Australian intermittently open estuary

Recruitment and growth of juvenile yellowfin bream, Acanthopagrus australis Günther (Sparidae), an economically important species, were examined in an intermittently open Australian estuary for 13 months. Fish had a mean fork length of 77.9 (± SE 9.5) mm after 1 year. Growth rates were faster than those found in previous studies in permanently open estuaries and appeared to be dependent upon the water temperature, which ranged from 0.04 mm/day in winter to 0.67 mm/day during summer. However, periods of slower growth may also reflect the emigration of larger fish from the cohort when the estuary was open and which coincided with lower water temperatures. Growth and length-at-age of fish using length-frequency data may be estimated more accurately in intermittently open estuaries because the time of recruitment can be determined, especially when the estuary opening period is short.     

Exceptional growth rates of captive loggerhead sea turtles,Caretta caretta

Twelve loggerhead sea turtle hatchlings (Caretta caretta) were removed from a nest site (A) at the Back Bay National Wildlife Refuge (U.S. Fish and Wildlife Service), Virginia Beach, VA. Hatchlings were distributed among study participants, and raised in captivity for a period of two years. Growth of the loggerheads was recorded weekly by straight-line caliper measurements of carapace lengths as well as measurements of total weights. Growth rates from the present study were much greater than those measured in previous studies. Mean weights for Nest A turtles at 1.5 years ranged from 10.3 to 17.6 kg, with one exceptional individual reaching 20.0 kg. The data from this study provide new insights into the early growth potential of loggerhead sea turtles. How this accelerated development may affect sexual maturity and post-release viability remain to be determined. © 1993 Wiley-Liss, Inc.     

Developmental stage of failed eggs in the red-legged partridge <Emphasis Type="Italic">Alectoris rufa</Emphasis>

Understanding whether egg failure occurs more frequently during laying or during incubation is important for determining the most vulnerable period of the egg phase in bird species with long laying and incubation periods. However, most studies compare nest failure during the egg stage and the hatchling stage. In this study we examined whether egg failure was higher during the laying period and early development than during the final stages of development in a population of red-legged partridge (Alectoris rufa) from northeast Spain. We collected 216 abandoned eggs in the field. Only 12% (n = 26) of the eggs were sufficiently intact to enable direct assessment of developmental stage, showing that 81% of 26 eggs were lost during early stages. The majority of eggs were depredated (n = 154, 71%), as evidenced by an opening hole. To take advantage of information contained in these eggs, we propose a simple method to assess their developmental stage by measuring the size of the opening of their hole. Based on this method, we estimated that the proportion of eggs lost during early stages ranged from 72 to 83%. We validated this result of a high percentage of egg failure during early developmental stages with a larger experimental sample. Nest losses in the partridge are higher during the laying period or early development. This result is important in that the direction of conservation efforts and their seasonal application should be adjusted to account for the most important factors affecting egg failure.     

Structure and grazing impact of the protozooplankton community in the waters surrounding the Prince Edward Islands (Southern Ocean)

Fish <1 year old were sampled during 1 year using nets inshore at South Georgia. Some fish were kept in aquaria. Growth rates were estimated using the exponential model. During June to October 1980, field growth rates of Parachaenichthys georgianus and Champsocephalus gunnari were 0.33 and 0.48% SL day⁻¹, respectively. Gobionotothen marionensis (1979 cohort) grew at 0.40% SL day⁻¹ during June to November in the field, and 0.34% SL day⁻¹ in the laboratory from September to March. Notothenia coriiceps grew at 0.28% SL day⁻¹ in the laboratory during September to March. During November to December, Artedidraco mirus grew at 0.82% SL day⁻¹ in the field. The 1980 cohort of G. marionensis grew at 1.39% SL day⁻¹ during November to January in the field. During January, the field growth rate of G. gibberifrons was 1.39% SL day⁻¹. Growth rates increased three-fold from winter to summer. Temperature can only explain one-half of this range in growth rates, whereas all of this range can be explained by food availability. Therefore, seasonal food resource limitation has a major effect on Antarctic fish growth. Received: 30 June 1997 / Accepted: 7 September 1997     

Early development of the skull of Sander lucioperca (L.) (Teleostei: Percidae) relating to growth and mortality

The early osteological development of the skull (chondrocranium and osteocranium) of the pikeperch Sander lucioperca was studied. Specimens were reared at two temperatures, 15·5 and 18·0° C, from hatching until 47 and 43 days after fertilization (DAF), respectively. The skeletal elements characteristic for the different developmental stages were the same at both rearing temperatures, but pikeperch reared at 15·5° C reached the developmental stages later. The formation of the functional complexes, the neurocranium, jaws and suspensorium, branchial basket and hyoid arch, was evaluated chronologically. The focus was on skull development during several functional changes: at hatching, at the shift from endogenous to mixed feeding, the shift to exclusively exogenous feeding and upon reaching the final prey-capture mechanism. Growth in total length differed between fishes reared at the two temperatures, except during a phase of very slow growth from the end of the embryonic stage until the second larval stage. The latter phase, in which most of the bony elements of the viscerocranium started to form, was marked by high mortality. When exogenous feeding began, the growth rates at both temperatures increased distinctly and the first bony elements were formed in the neurocranium. Specimens reared at 18·0° C grew continuously, but those at 15·5° C showed a second period of slow growth and high mortality. Fish reared at 18·0° C reached the successive larval stages distinctly earlier than fish reared at 15·5° C.     

Phytoplankton growth rates in the Ross Sea, Antarctica, determined by independent methods: temporal variations

The development of the seasonal phytoplankton bloom in the Ross Sea was studied during two cruises. The first, conducted in November-December 1994, investigated the initiation and rapid growth of the bloom, whereas the second (December 1995-January 1996) concentrated on the bloom's maximum biomass period and the subsequent decline in biomass. Central to the understanding of the controls of growth and the summer decline of the bloom is a quantitative assessment of the growth rate of phytoplankton. Growth rates were estimated over two time scales with different methods. The first estimated daily growth rates from isotropic incorporation under simulated in situ conditions, including ¹⁴C, ¹⁵N and ³²Si uptake measurements combined with estimates of standing stocks of particulate organic carbon, nitrogen and biogenic silica. The second method used daily to weekly changes in biomass at selected locations, with net growth rates being estimated from changes in standing stocks of phytoplankton. In addition, growth rates were estimated in large-volume experiments under optimal irradiances. Growth rates showed distinct temporal patterns. Early in the growing season, short-term estimates suggested that growth rates of in situ assemblages were less than maximum (relative to the temperature-limited maximum) and were likely reduced due to low irradiance regimes encountered under the ice. Growth rates increased thereafter and appeared to reach their maximum as biomass approached the seasonal peak, but decreased markedly in late December. Differences between the major taxonomic groups present were also noted, especially from the isotopic tracer experiments. The haplophyte Phaeocystic antarctica was dominant in 1994 throughout the growing season, and it exhibited the greatest growth rates (mean 0.41 day^-1) during spring. Diatom standing stocks were low early in the growing season, and growth rates averaged 0.100 day^-1. In summer diatoms were more abundant, but their growth rates remained much lower (mean of 0.08 day^-1) than the potential maximum. Understanding growth rate controls is essential to the development of predictive models of the carbon cycle and food webs in Antarctic waters.      

The influence of temperature during early life on phenotypic expression at later ontogenetic stages in sea bass

To exam whether the temperature experienced by fishes at early developmental stages can influence their phenotype at subsequent stages, the model species used, European sea bass Dicentrarchus labrax was subjected to water temperatures of 15 or 20° C during the half-epiboly stage until the metamorphosis. Meristic and morphometric characters at three different stages, well after the end of the thermal treatments, were explored. Body shape and most of the meristic characters were significantly affected by the environmental temperature during their early life stages. Fish body shape at 15° C tended to be more slender than at 20° C. The dorsal spines and soft rays, the pectoral lepidotrichia and caudal dermatotrichia were significantly affected. Phenotypic differences due to the two thermal regimes are discussed in terms of their functional meaning during the transition from the planktonic to the littoral niche.     

The ecology of young turbot, Scophthalmus maximus (L.), at Borth, Cardiganshire, Wales

The ecology of 0- and 1-group turbot was studied at Borth, Cardiganshire, during the years 1966–68. Newly-metamorphosed turbot appeared in the surf zone from July to October, Abundance during the period September 1967 to May 1968 decreased at an average rate of 25% of the sampled population per month. Fish of the 1966 year-class grew from a mean length of 4.5 cm in September 1966 to 14.4 cm in October 1967. Growth was fast in the spring and summer, slowing during the late autumn and winter. The most important food items of 0- and 1-group turbot by percentage occurrence and dry weight were polychaetes and mysids. The daily food intake of 0-group turbot in September 1967 was estimated as 2.5 % of the body weight per day.     

长江口水域夏季鱼卵和仔稚鱼年间变化

基于2005年、2008年、2009年和2011年8月(夏季)在长江口水域(30°30'—31°45'N,121°15'—123°10'E)4个航次的浮游生物拖网资料,分析了长江口水域鱼卵和仔稚鱼的种类组成、数量分布特征及其年间变化。结果表明:4个航次采集的鱼卵和仔稚鱼鉴定到种的种类有17种,隶属于8目13科,以鲈形目种类最多,11种,其次是鲱形目,5种,其他各目种类均小于5种;种类数存在明显年间差异,2005年种类数最多(鱼卵3种,仔稚鱼8种),其次是2009年和2011年,2008年种类数最少(鱼卵1种,仔稚鱼5种)。优势种年间更替明显,长蛇鲻(Saurida elongata)、虾虎鱼(Gobiidae spp.)和中华小公鱼(Stolephorus chinensis)在2005年是优势种,2008年优势种为鳀鱼(Engraulis japonicus),2009年优势种为鳀鱼、寡鳞飘鱼(Pseudolaubuca engraulis)、虾虎鱼等,2011年虾虎鱼和小公鱼(包括小公鱼属未定种Stolephorus spp.和中华小公鱼Stolephorus chinensis)成为优势种。2005年鱼卵和仔稚鱼数量分布的密集区在嵊泗列岛附近水域,2008年鱼卵和仔稚鱼出现较少,未出现明显的数量密集区;2009年鱼卵数量较少,仔稚鱼数量较多,密集区主要分布在在长江口以外123°E附近水域;2011年鱼卵主要分布在在长江北支口门外附近水域,仔稚鱼在调查区内分布相对均匀。     

Length–weight relationships of two mugilid species from tropical estuarine systems in Alagoas,northeastern coast of Brazil

Length‐weight relationships were estimated for two mugilid species from estuarine systems in Alagoas, northeastern Brazil. Fish were sampled monthly using nylon monofilament gillnets with different mesh sizes during two fishery surveys. The first LWR reference for Mugil curvidens and new maximum lengths for both M. rubioculus and M. curvidens are provided.     

The timing of early life events and growth rate estimates of age‐0 year group brill Scophthalmus rhombus along the west coast of Ireland

The timing of spawning and hatching, larval durations and growth exhibited by juvenile brill Scophthalmus rhombus captured along the Irish west coast were estimated using otolith microstructure analysis. Scophthalmus rhombus were estimated to have hatched between February and May, with fish settling onto nursery grounds between March and June. Fish collected later on in the season exhibited higher otolith growth rates in comparison to earlier collected fish. This is the first study to describe the early life history of a commercially valuable but understudied flatfish species.     

GROWTH INHIBITION IN GAMETOPHYTES AND OAT COLEOPTILES BY THELYPTERIN A AND B RELEASED FROM ROOTS OF THE FERN THELYPTERIS NORMALIS

Gametophytes, when grown in the immediate vicinity of a Thelypteris normalis sporophyte—in soil or in sterile culture on agar—showed a reduced number of cells and an altered gross morphology. This is attributed to the action of the thelypterins, which are inhibitors released from T. normalis sporophytes. Growth inhibition of the gametophytes was greatest when thelypterins were added during early stages of gametophyte development. Removal of thelypterin A permitted resumption of growth. Thelypterin A noncompetitively inhibited auxin-enhanced elongation of A vena coleoptiles. The growth of T. normalis root segments was not affected by thelypterins. The growth of young sporophytes of T. normalis was inhibited by mature sporophytes.     

Embryonic duration and post-embryonic growth rates of the tropical freshwater shrimp Caridina nilotica (Decapoda:Atyidae) under laboratory and experimental field conditions

SUMMARY. Embryonic durations and post embryonic growth rates of Caridina nilotica were determined under laboratory conditions at constant temperatures near 18, 24 and 30°C. Embryonic durations and intermoult intervals were negative curvilinear functions of temperature. At a given temperature moulting frequency varied inversely with shrimp size and slight sexual differences were apparent. Moulting frequency of berried females was governed by the temperature-specific embryonic durations. Growth rates were determined from changes in carapace length (CL) of individual shrimps (laboratory) or batches of shrimps (field enclosures) over 1 month and these data were used to calculate temperature-specific life-long growth curves for males and females. Growth in body mass was estimated indirectly from the carapace length-mass relationship of C. nilotica. On average, males grew marginally faster than females during the first 2 months of life, but growth of males larger than CL= 4 mm was considerably depressed relative to that of females. Inflexions in growth rate, apparently related to the onset of sexual maturity, were apparent in both sexes. Under laboratory conditions, the growth rate of males increased with temperature, but temperature-related differences were not as marked in females. Notwithstanding the more rapid moulting rate at 30°C the growth rate of females was slightly slower at 30 than at 24°C as a result of marginally but significantly smaller per moult growth increments observed at 30°C in animals up to CL= 5.5 mm. Possible reasons for this depressed growth are discussed. Growth rates of animals in field enclosures in Lake Sibaya over 1 month in winter (20 ± 3°C) were generally comparable to those estimated for the 18°C laboratory experiments. Growth rates in enclosures containing tripled standing stocks were almost identical to those containing the naturally occurring biomass of animals, suggesting a non-limited environment at least during the time of the experiment.     

A density-dependent model of Cirsium vulgare population dynamics using field-estimated parameter values

Two versions of a stage-structured model of Cirsium vulgare population dynamics were developed. Both incorporated density dependence at one stage in the life cycle of the plant. In version 1 density dependence was assumed to operate during germination whilst in version 2 it was included at the seedling stage. Density-dependent parameter values for the model were estimated from annual census data in a factorial grazing experiment. Version 1 of the model produced significant estimates of density dependence under field conditions. The estimated values, when included in a simulation of the dynamics, produced two-point limit cycles under conditions of hard grazing. The limit cycles were most pronounced at the early rosette stage. Comparison of the effects of density dependence at the two different stages in the life cycle revealed a strong difference in predicted dynamics. This emphasizes the importance of determining where density dependence operates under field conditions and the potential problems of arbitrarily assigning it to particular life-history stages. Version 1 of the model produced a good prediction of observed mean plant density across the different grazing treatments (r ²=0.81, P<0.001).     

The growth of some Ephemeropteran nymphs during winter in a North Swedish River

The growth of the Ephemeroptera species Heptagenia fuscogrisea Retzius, Leptophlebia marginata L. and Ephemerella mucronata Bengtsson was studied from the middle of September 1967 to the middle of May 1968 in the River Rickleån in northern Sweden. Sampling was performed also during periods with ice cover. Growth was estimated from four different body measures and proceeded fairly steady through all the winter for the three species. There were no indications of changed body proportions during the investigation period.     

Carbon Metabolism Transitions during the Development of Marine Macroalga Gracilaria verrucosa

The changes in the rate of photosynthetic and dark CO₂ assimilation and the activity of key enzymes of carboxylation were studied during the main developmental stages (shoots, juvenile plants, and mature plants) of red macroalga Gracilaria verrucosa (Huds.) Papenf. Changes in the direction of primary carbon metabolism were also investigated. It was estimated that the transition of metabolism related to the shift in the pathways of carboxylation did not occur during development of G. verrucosa. During all developmental stages, the level of dark CO₂ assimilation was by at least one order of magnitude lower than that of photosynthetic assimilation The predominant pathway of CO₂ assimilation was ribulosobisphosphate carboxylation. At the same time, the transition of metabolism related to the changes in the type of phosphoglyceric acid utilization was found. At the early developmental stages, a substantial part of phosphoglyceric acid was directed into the amino acid metabolism via the anaplerotic pathway of photosynthesis similar to that in higher plants.     

Microgeographical diversification of threespine stickleback: body shape–habitat correlations in a small, ecologically diverse Alaskan drainage

Adaptive radiations are a major source of evolutionary diversity in nature, and understanding how they originate and how organisms diversify during the early stages of adaptive radiation is a major problem in evolutionary biology. The relationship between habitat type and body shape variation was investigated in a postglacial radiation of threespine stickleback in the upper Fish Creek drainage of Cook Inlet, Alaska. Although small, the upper Fish Creek drainage includes ecologically diverse lakes and streams in close proximity to one another that harbour abundant stickleback. Specimens from ancestral anadromous and derived resident freshwater populations differed substantially and could be distinguished by body shape alone, suggesting that the initial stages of adaptation contribute disproportionately to evolutionary divergence. Body shape divergence among resident freshwater populations was also considerable, and phenotypic distances among samples from freshwater populations were associated with habitat type but not geographical distance. As expected, stream stickleback from slow-moving, structurally complex environments tended to have the deepest bodies, stickleback from lakes with a mostly benthic habitat were similar but less extreme, and stickleback from lakes with a mostly limnetic habitat were the most shallow-bodied, elongate fish. Beyond adapting rapidly to conditions in freshwater environments, stickleback can diversify rapidly over small geographical scales in freshwater systems despite opportunities for gene flow. This study highlights the importance of ecological heterogeneity over small geographical scales for evolutionary diversification during the early stages of adaptive radiation, and lays the foundation for future research on this ecologically diverse, postglacial system.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 139–151.